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#pragma once
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#ifndef TCG_CONTROLLED_ACCESS_H
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#define TCG_CONTROLLED_ACCESS_H
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// tcg includes
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#include "base.h"
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/*!
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  \file     controlled_access.h
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  \brief    This file contains the description of a C++ idiom that can be used
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            to perform controlled access on an object.
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  \details  Controlled access forces users to invoke a function every time an
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            object is accessed, at compile-time.
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            Some notable cases for this idiom include the "frequent notifier / lazy update"
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            scenario, where an object is frequently notified for status updates, but
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            many updates can be spared until the data is finally accessed.
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*/
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namespace tcg
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{
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enum DirectAccess { direct_access }; //!< Enum used to access variables with
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									 //!  controlled output directly.
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//*************************************************************************
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//    tcg::controlled_access  definition
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//*************************************************************************
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/*!
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  \brief    The controlled_access template class encapsulate an object that
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            can be accessed \b only after a functor has been invoked, enforcing
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            access tracking at compile time.
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  \details  The accessor functor can be specified by explicit template argument
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            or supplying it during access. In case the accessor type is specified,
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            an instance of the functor will be stored together with the accessed
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            variable.
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  \todo     Move functor to base class to enable empty class optimization for
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            stateless functors.
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*/
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template <typename func="tcg::empty_type" obj,="" typename=""></typename>
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class controlled_access : tcg::noncopyable<>
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{
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	Obj m_obj;   //!< Stored object.
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	Func m_func; //!< Functor to be invoked upon access.
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public:
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	typedef Obj obj_type;
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	typedef Func func_type;
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public:
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	controlled_access(const func_type &func) : m_obj(), m_func(func) {}
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	controlled_access(const obj_type &obj, const func_type &func)
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		: m_obj(obj), m_func(func) {}
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	const obj_type &operator()(DirectAccess) const { return m_obj; }
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	obj_type &operator()(DirectAccess) { return m_obj; }
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	const obj_type &operator()() const
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	{
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		m_func(m_obj);
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		return m_obj;
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	}
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	obj_type &operator()()
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	{
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		m_func(m_obj);
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		return m_obj;
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	}
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};
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//------------------------------------------------------------------------------
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/*!
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  \brief    Explicit specialization advocating no explicit accessor functor - the
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            accessor must be supplied upon access.
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*/
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template <typename obj=""></typename>
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class controlled_access<obj, tcg::empty_type=""> : tcg::noncopyable<></obj,>
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{
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	Obj m_obj; //!< Stored object.
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public:
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	typedef Obj obj_type;
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public:
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	controlled_access() : m_obj() {}
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	controlled_access(const obj_type &obj) : m_obj(obj) {}
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	const obj_type &operator()(DirectAccess) const { return m_obj; }
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	obj_type &operator()(DirectAccess) { return m_obj; }
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	template <typename func=""></typename>
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	const obj_type &operator()(Func func) const
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	{
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		func(m_obj);
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		return m_obj;
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	}
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	template <typename func=""></typename>
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	obj_type &operator()(Func func)
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	{
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		func(m_obj);
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		return m_obj;
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	}
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};
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//==============================================================================
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/*!
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  \brief    The invalidable template class is a common case of controlled variable
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            access for objects which can be \a invalidated, and thus require a validator
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            procedure to be invoked strictly before a user access to the object can be
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            allowed.
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  \details  An invalidable instance wraps a \a mutable object and adds a boolean to
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            signal its current validity state.
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            The initial validity of the object can be specified at construction, and
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            explicitly set to the invalid state through the invalidate() method.
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            Access to the wrapped object requires either the invocation a validator
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            functor through the various operator() overloads, or that the access is
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            explicitly marked as \a direct by supplying the \p tcg::direct_access tag.
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*/
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template <typename func="tcg::empty_type" obj,="" typename=""></typename>
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class invalidable : tcg::noncopyable<>
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{
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	mutable Obj m_obj;		//!< Stored object.
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	mutable bool m_invalid; //!< Data validity status.
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	Func m_func; //!< Functor to be invoked upon access.
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public:
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	typedef Obj obj_type;
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	typedef Func func_type;
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public:
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	invalidable(const func_type &func, bool invalid = false)
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		: m_obj(), m_func(func), m_invalid(invalid) {}
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	invalidable(const obj_type &obj, const func_type &func, bool invalid = false)
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		: m_obj(obj), m_func(func), m_invalid(invalid) {}
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	void invalidate() { m_invalid = true; }
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	bool isInvalid() const { return m_invalid; }
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	const obj_type &operator()(DirectAccess) const { return m_obj; }
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	obj_type &operator()(DirectAccess) { return m_obj; }
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	const obj_type &operator()() const
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	{
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		if (m_invalid)
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			m_func(m_obj), m_invalid = false;
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		return m_obj;
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	}
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	obj_type &operator()()
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	{
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		if (m_invalid)
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			m_func(m_obj), m_invalid = false;
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		return m_obj;
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	}
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};
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//------------------------------------------------------------------------------
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/*!
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  \brief    Explicit specialization advocating no explicit validator functor - the
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            accessor must be supplied upon access.
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*/
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template <typename obj=""></typename>
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class invalidable<obj, tcg::empty_type=""> : tcg::noncopyable<></obj,>
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{
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	mutable Obj m_obj;		//!< Stored object
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	mutable bool m_invalid; //!< Data validity status
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public:
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	typedef Obj obj_type;
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public:
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	invalidable(bool invalid = false)
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		: m_obj(), m_invalid(invalid) {}
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	invalidable(const obj_type &obj, bool invalid = false)
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		: m_obj(obj), m_invalid(invalid) {}
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	void invalidate() { m_invalid = true; }
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	bool isInvalid() const { return m_invalid; }
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	const obj_type &operator()(DirectAccess) const { return m_obj; }
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	obj_type &operator()(DirectAccess) { return m_obj; }
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	template <typename func=""></typename>
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	const obj_type &operator()(Func func) const
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	{
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		if (m_invalid)
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			func(m_obj), m_invalid = false;
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		return m_obj;
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	}
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	template <typename func=""></typename>
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	obj_type &operator()(Func func)
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	{
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		if (m_invalid)
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			func(m_obj), m_invalid = false;
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		return m_obj;
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	}
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};
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} // namespace tcg
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#endif // TCG_CONTROLLED_ACCESS_H